The present invention relates to apparatus for processing CCD (charge coupled device) output signals, and more particularly, to such devices that have an integrated MOSFET (metal oxide semiconductor field effect transistor) amplifier.
When using a CCD imager, the output signal is derived from a clocked "C" register. The output charge signal generally is sensed with a low capacitance floating diffusion or gate to generate a voltage change which is buffered by a MOSFET amplifier which is integrated onto the same chip as that in which the imager is formed. However, such transistors have a large 1/f noise, i.e., the noise energy per unit of bandwidth increases as frequency decreases. In particular, this noise is especially troublesome from D.C. to a few kilohertz and causes random streaks in the displayed image.
It is therefore desirable to process the output signal from a CCD device to maximize the signal-to-noise ratio, which thereby reduces streaking in the displayed image if said device is an imager.